Things are moving along on this, there have been a few changes to the circuit posted in this thread on the third of this month, mostly minor so there's no point in re-posting it again (yet). The most obvious change is the removal of the 525/625 input standard switch, the micro now auto-detects which standard is to be converted.
A left-right pan-pot has been added to select which part of the FSTV frame is to be converted due to the difference in aspect ratios.
The input circuit is virtually unchanged from the design of long ago, but as above there are bound to be a few alterations. This has a 2MHz 75-ohm low-pass filter to suppress any colour subcarrier on the input signal, and also performs FSTV pulse extraction with black-level clamping of the video.
The memory within the micro is enough to store two 32x48 pixel NBTV frames [1], if need be, along with the required 'housekeeping' RAM.
As ever, anything in a colour aside from black means it's not 'set in stone' yet and may change...
Also, here's the plot of the input filter, despite its simplicity it does quite a good job...plus the following LF356 at a nominal gain of 3.6 will add a gentle roll-off starting at around 1.4MHz.
Steve A.
The PIC internal RAM usage is also below...you would be correct if you guess that I haven't started on the software yet...
[1] If (a big IF) only one frame store is required the line resolution
could be increased to 64 pixels, perhaps more...